linux-kernel - Re: [PATCH] tracing/events: Add bounce tracing to swiotbl-xen

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Message-ID: <20130904203502.GA8726@phenom.dumpdata.com>
Date:	Wed, 4 Sep 2013 16:35:03 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Zoltan Kiss <zoltan.kiss@...rix.com>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xensource.com,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] tracing/events: Add bounce tracing to swiotbl-xen

On Wed, Sep 04, 2013 at 09:10:50PM +0100, Zoltan Kiss wrote:
> On 03/09/13 13:42, Konrad Rzeszutek Wilk wrote:
> >Correct. The double buffering code is being run in lib/swiotlb.c not the
> >xen-swiotlb.c. Hence the question of why not move the tracing in there.
> I've put the trace to both locations before swiotlb_tbl_map_single
> is called, so the same tracer will be hit both with classic and Xen
> SWIOTLB. I used 2 different place instead of calling from
> swiotlb_tbl_map_single because I want to print out dev_addr, and
> it's calculated differently.
> 
> >Yes. And please (if it adds a benefit) also for unmap/sync which can trigger
> >the bounce buffer.
> >
> >Or if it makes sense just for the bounce buffer copying - then just
> >leave it at that. Thanks.
> For me the relevant event was to see when we start to do bounce
> buffering. When does it end, or when syncing happens is a different
> thing. If someone is interested, they can easily extend this patch
> with that.
> 
> However one question bothers me: why ftrace doesn't trace these
> functions? They are not inlined, static, or marked as notrace.

They are usually part of the dma_ops structure. That might be the reason.
> 
> Regards,
> 
> Zoli
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